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Surface Water Ground-Source Heat Pump Systems
Published in Vasile Minea, Heating and Cooling with Ground-Source Heat Pumps in Cold and Moderate Climates, 2022
The enthalpy (latent heat) of fusion (melting) is the change in water enthalpy resulting from providing heat to 1 kg of water to change its state from solid to liquid at constant pressure. For example, when melting 1 kg of ice at 0°C and atmospheric pressure assumed by convention to be 101,325 kPa, 333.55 kJ of heat is absorbed with no temperature change.
Energy, Environment, and Renewable Energy
Published in Radian Belu, Fundamentals and Source Characteristics of Renewable Energy Systems, 2019
Enthalpy is very useful in describing the heat transfer at constant pressure (e.g., in boilers, or condensers), where the change in the enthalpy is equal to the heat input, or in adiabatic (Q = 0) compression or expansion (e.g., compressors and turbines), where the network on the shaft is equal to the change in the enthalpy. The concept of entropy arises from the second and is a measure of the degree of disorder of a system. From a thermodynamic point of view there are two types of processes: reversible and irreversible processes. In the first one, the system and the surroundings can recover their initial states by changing the system slowly enough that it remains in a quasi-static thermal equilibrium throughout the process. In irreversible process the system and the surroundings are changed in such away that they are not able to return to their original states. Mathematically the entropy change is expressed as: () Δs=ΔQrevT
The Conservation Equations of Fluid Mechanics
Published in Robert E. Masterson, Nuclear Reactor Thermal Hydraulics, 2019
Here, both the internal energy u and the flow work pυ are expressed on a per mass basis and υ is the specific volume of the fluid measured in m3/kg. In the SI unit system, the specific enthalpy is measured in J/kg or kJ/kg. So in principle, it is easy to see that the equation for the conservation of energy can be written as
Thermal management and develop energy storage in performance improvement of triangular and cubical parabolic collectors
Published in Numerical Heat Transfer, Part A: Applications, 2023
Samaneh Baharloui, Mofid Gorji Bandpy
In thermodynamics, the enthalpy is the measure of energy in a thermodynamic system. It is the thermodynamic quantity equal to the complete heat content of a system. The enthalpy is described to be the sum of the inner energy E plus the product of the stress P and quantity V. In many thermodynamic analyses the sum of the internal strength U and the product of pressure P and quantity V appears, consequently it is handy to supply the combination a name, enthalpy, and an awesome symbol, H. Figure 9, illustrated the maximum enthalpy in triangular collector with water, oil, ethylene glycol, and glycerin fluids are 289,682.97, 280,459.62, 28,115.92, and 279,530.99j/kg, respectively. According to Figure 9, the maximum enthalpy in cubical collector using water, oil, ethylene glycol, and glycerin fluids are 285,160.95, 215,510.97, 224,122.95 and 216,187.99 respectively. Also, Figure 10, illustrated that the enthalpy performance of triangular collector for oil, ethylene glycol, and glycerin fluids are 12%, 26%, and 30%, respectively.
Physicochemical Characterization and Chemical Reactivity of Biochar from Pyrolysis of Dried Distiller’s Grains with Solubles (DDGs)
Published in Combustion Science and Technology, 2023
Danlan Cui, Xin Zheng, Jianfeng Zou, Shirui Yu, Xiao Kong, Junmeng Cai, Xingguang Zhang
Thermodynamic analysis plays an important role in the thermochemical conversion efficiency of biomass. The corresponding thermodynamic parameters reflect the thermodynamic characteristics and reveal reaction complexity of biomass thermochemical conversion processes (Nawaz and Kumar 2022). Enthalpy change is the property of system thermodynamics, which indicates the energy difference between the product and reactant in the chemical reaction. For biomass pyrolysis processes, enthalpy change indicates the energy required when biomass is decomposed into products during pyrolysis (Gupta, Gupta, and Mondal 2020). The randomness and spontaneity in the system are determined by entropy change. The larger the entropy change, the higher the reactivity of the reactant. The change in Gibbs free energy represents the total energy required to activated complexes during its formation. The higher the value of ∆G, the greater the energy required in the pyrolysis process (Nawaz and Kumar 2021). These thermodynamic parameters can convey the energy requirements in the pyrolysis process and thus are necessary to study the pyrolysis behavior of substances.
Lamellar structure silver sulfide nanoparticles for adsorption and selective separation of zirconium, yttrium and strontium ions
Published in Journal of Dispersion Science and Technology, 2022
Hoda E. Rizk, Mohamed F. Attallah, Amal M. Ali
The tabulated data in Table 2 show that the adsorption process is exothermic with ΔH values equal − 41.84 and −16.23 kJ/mol for adsorption of zirconium and yttrium ions, respectively. The change in enthalpy of a reaction is measured by the differences between the enthalpy of the reactants and products. Enthalpy of reactants due to the dehydration of metal ions from their complex is an endothermic process, favored with high temperature; on the other hand, contact of metal ions with the surface of the sorbent is an exothermic process.[52] The negative values of the change in enthalpy for adsorption of Zr(IV) and Y(III) indicate that the energy of attachment of metal ions on the surface of Ag2S exceeds the endothermicity of the dehydration process.